中国物理B ›› 2025, Vol. 34 ›› Issue (8): 88708-088708.doi: 10.1088/1674-1056/adbdbf

所属专题： SPECIAL TOPIC — A celebration of the 90th Anniversary of the Birth of Bolin Hao

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Force-dependent unfolding dynamics of spectrin R16: Resolving experimental contradiction and unveiling model consistency

Wanxing Zhang(张万星)1, Zhuwei Zhang(张珠伟)1,2, Zhenyong Xue(薛振勇)1,2, Yuhang Zhang(张宇航)1,2, Shimin Le(乐世敏)1,†, and Hu Chen(陈虎)1,2,‡   

  1. 1 Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Laboratory for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen 361005, China;
    2 Center of Biomedical Physics, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, China
  • 收稿日期:2024-12-28 修回日期:2025-02-06 接受日期:2025-03-07 出版日期:2025-07-17 发布日期:2025-07-17
  • 通讯作者: Shimin Le, Hu Chen E-mail:leshimin@xmu.edu.cn;chenhu@xmu.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 12174322, 12474200, 32271367, and 12204389), 111 Project (B16029), and Research Grant from Wenzhou Institute.

Force-dependent unfolding dynamics of spectrin R16: Resolving experimental contradiction and unveiling model consistency

Wanxing Zhang(张万星)1, Zhuwei Zhang(张珠伟)1,2, Zhenyong Xue(薛振勇)1,2, Yuhang Zhang(张宇航)1,2, Shimin Le(乐世敏)1,†, and Hu Chen(陈虎)1,2,‡   

  1. 1 Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Laboratory for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen 361005, China;
    2 Center of Biomedical Physics, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, China
  • Received:2024-12-28 Revised:2025-02-06 Accepted:2025-03-07 Online:2025-07-17 Published:2025-07-17
  • Contact: Shimin Le, Hu Chen E-mail:leshimin@xmu.edu.cn;chenhu@xmu.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 12174322, 12474200, 32271367, and 12204389), 111 Project (B16029), and Research Grant from Wenzhou Institute.

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摘要： Spectrin domains, characterized by a distinctive triple helix structure, are crucial in physiological processes, particularly in maintaining membrane shape and crosslinking cytoskeletons. Previous research on the 16th domain of $\alpha$-spectrin repeats (R16) has yielded conflicting results: bulk experiments showed an unfolding rate approximately two orders of magnitude faster than the zero-force result extrapolated from single-molecule force spectroscopy experiments using atomic force microscopy (AFM). To address this discrepancy, we investigated the folding and unfolding rates of R16 across a broader range of forces using magnetic tweezers (MT). Our findings reveal that AFM results at higher forces cannot be directly extrapolated to the low-force regime due to a nonlinear relationship between force and the logarithm of the unfolding rate. We demonstrated that two-dimensional model, structural-elastic model, and two-pathway model can all effectively explain the experimental data when they capture the core physics of the short unfolding distance at low forces. Our study provides a more comprehensive understanding of the unfolding dynamics of the spectrin domain, resolves previous contradictory experimental results, and highlights the common basis of different theoretical models.

关键词: spectrin, protein folding and unfolding, force spectroscopy, magnetic tweezers

Abstract: Spectrin domains, characterized by a distinctive triple helix structure, are crucial in physiological processes, particularly in maintaining membrane shape and crosslinking cytoskeletons. Previous research on the 16th domain of $\alpha$-spectrin repeats (R16) has yielded conflicting results: bulk experiments showed an unfolding rate approximately two orders of magnitude faster than the zero-force result extrapolated from single-molecule force spectroscopy experiments using atomic force microscopy (AFM). To address this discrepancy, we investigated the folding and unfolding rates of R16 across a broader range of forces using magnetic tweezers (MT). Our findings reveal that AFM results at higher forces cannot be directly extrapolated to the low-force regime due to a nonlinear relationship between force and the logarithm of the unfolding rate. We demonstrated that two-dimensional model, structural-elastic model, and two-pathway model can all effectively explain the experimental data when they capture the core physics of the short unfolding distance at low forces. Our study provides a more comprehensive understanding of the unfolding dynamics of the spectrin domain, resolves previous contradictory experimental results, and highlights the common basis of different theoretical models.

Key words: spectrin, protein folding and unfolding, force spectroscopy, magnetic tweezers

中图分类号:  (Single molecule manipulation of proteins and other biological molecules)

  • 82.37.Rs
87.14.E- (Proteins) 87.15.hm (Folding dynamics) 87.80.Nj (Single-molecule techniques)